This invention relates to a caster of the single wheel type having a wheel lock function.
U.S. Pat. Nos. 3,571,842 and 3,772,733 disclose lock mechanisms for a single wheel-type caster. This lock mechanism includes a push button, and the push button is operated to move a friction member toward an outer peripheral surface of a wheel, thereby locking the wheel utilizing the friction between the friction member and the outer peripheral surface of the wheel. The push button is held in a wheel-locking position and in a wheel-unlocking position by a hold mechanism. However, since the lock mechanism of this construction depends for its locking function on the frictional force, the locking of the wheel is not entirely satisfactory, and it is difficult to stably stop the wheel.
U.S. Pat. No. 4,479,566 discloses a wheel lock mechanism in a double wheel-type caster. This caster includes a frame having one vertical support wall. A pair of wheels are arranged on the opposite sides of the support wall, respectively, and are rotatably supported by the support wall. The lock mechanism includes a number of engagement recesses formed in each of the pair of wheels, a push button supported on the support wall so as to move radially of the wheels, and a rotor rotatably supported on the push button. The opposite ends of the rotor are engaged respectively in the engagement recesses of the pair of wheels, thereby positively locking the pair of wheels. A hold mechanism for holding the push button includes a cam hole formed in the support wall, and a cam follower formed on the rotor intermediate the opposite ends of this rotor.
In the present invention, the basic principle of the lock mechanism of the above U.S. Pat. No. 4,479,566 is applied to a single wheel-type caster, and the present invention includes various improvements.